1. Field of the Invention
The present invention relates to a fusing apparatus for fusing a toner image onto paper. More particularly, the present invention relates to a fusing apparatus in an image forming apparatus that heats a fusing unit by applying an induced current. Flicker characteristics of the fusing apparatus are improved by gradually increasing the amount of induced current applied to the fusing unit for a predetermined amount of time so that the amount of induced current applied to the fusing unit is prevented from severely varying.
2. Description of the Related Art
A conventional image printing apparatus comprises a fusing apparatus that applies a predetermined pressure and amount of heat to toner in order to fuse the toner image onto paper. The fusing apparatus includes a fusing unit which applies a predetermined amount of heat to the toner and a pressurizer that applies a predetermined pressure to the toner. The fusing unit includes a heating body that generates heat used to fuse the toner image onto the paper and a fusing roller that transfers heat generated by the heating body onto the paper.
FIG. 1 shows a schematic cross-sectional view taken along a lateral plane through a fusing unit 10 of a conventional fusing apparatus using a halogen lamp as a heat source. Referring to FIG. 1, the fusing unit 10 comprises a fusing roller 11 and a heating body 12, which is a halogen lamp, installed in the center of the fusing unit 10. A coating layer 1 la made of Teflon is formed on the surface of the fusing roller 11. The heating body 12 generates heat, and the fusing roller 11 is heated by radiant heat transferred from the heating body 12.
FIG. 2 illustrates a functional block diagram of a conventional fusing apparatus using a halogen lamp as a heat source. Referring to FIG. 2, noise is filtered from the voltage input, power supply voltage 210, by passing the voltage through a line filtering unit 220. The filtered voltage is provided to a heating unit 250 of fusing roller 240. The heating unit 250 is resistance-heated by the filtered voltage input thereto, and heat generated by the heating unit 250 heats the fusing roller 240. The temperature of the fusing roller 240 is sensed by sensing unit 260. A control unit 270 controls the turning on or off of switch 230 with reference to the temperature of the fusing roller 240 sensed by sensing unit 260.
In a conventional fusing unit using a halogen lamp as a heat source, a warm-up time of several seconds to several minutes is required to supply sufficient energy and heat to the fusing roller 11 so that the fusing roller 11 reaches a target fusing temperature. Thus, a user should wait for a long warm-up time when printing an image.
In conventional fusing units, the amount of current flowing in a heating unit is determined by the voltage applied to the heating unit. However, when voltage is applied to the heating unit, the amount of current input to the heating unit drastically increases, thereby causing deteriorating flicker characteristics.